This invention relates to apparatus and methods for manufacturing improved thin-film magnetic recording transducers, commonly referred to as recording transducers. More specifically, it relates to a focused particle beam system for milling a portion of a pole-tip assembly of the recording transducer without irradiating a sensitive structure, e.g. a read head, of the recording transducer.
Thin-film magnetic recording transducers have gained wide acceptance in the data storage industry. A recording transducer includes a write head and a read head. The recording transducer has an air bearing surface that passes adjacent to a recording medium, such as a magnetic disk. The portions of the recording transducer, including portions of the write head and of the read head, that are proximate to the air bearing surface form a small, precisely shaped pole-tip assembly. The size and shape of the pole-tip assembly, which include features on the order of one-half a micron, in part determine the magnetic field pattern produced by the recording transducer. This magnetic field pattern effects how narrowly the recording transducer can record data tracks on the magnetic media of magnetic memory storage devices, such as computer hard disks, and digital data tape drives.
Thinner data tracks allow a storage device to store more data tracks per area of media and therefore more data per device. Accordingly, precisely forming the pole-tip assembly of the recording transducer results in an increase in the total data storage capacity of a magnetic memory device. Manufacturers seek to form the geometry of a pole-tip assembly with high precision, and consequently achieve pole-tip assemblies capable of providing magnetic field patterns suitable for writing narrow tracks of recorded data.
Manufacturers presently fabricate multiple recording transducers from a single multi-layer device, and endeavor to form the precise desired shape of the pole-tip assembly of a recording transducer by employing lithographic techniques in fabricating the multi-layer device. Typically, lithographic techniques deposit alternating layers of conductive and insulating materials onto a substrate by an evaporation, sputtering, plating, or other deposition technique that provides precise control of the deposition thicknesses. Chemical etching, reactive ion etching (RIE), or other techniques shape and form the deposited layers into a pole-tip assembly having the desired geometry. Thus, a multi-layer lithographicaly fabricated device can form a plurality of recording transducers having pole-tip assemblies.
Although existing lithographic techniques work sufficiently well to provide pole-tip assemblies having feature sizes suitable for current data storage capacity, these lithographic techniques are limited as to the small feature sizes that they can produce. For example, present photolithographic techniques require precise application of photoresist layers. Commonly, the photoresist layer is applied to produce a topology that includes voids having aspect ratios of 10:1 or larger. Such topologies are difficult to achieve reliably, at the desired small sizes, using such a photoresist technique.
Thus, these lithographic techniques are poorly suited for achieving a high yield of precisely formed, ultra-small, pole-tip assemblies. In the interest of increased storage density, manufacturers decrease the dimensions of a desired pole-tip assembly. As the dimensions of the desired pole-tip assembly decrease, manufacturers who use existing lithographic techniques experience yield loss. In other words, even if manufacturers using existing lithographic techniques are successful in achieving a desired pole-tip assembly configuration, they generally achieve that desired configuration with a low yield.
The kinds of defects that occur during the manufacturing process are difficult to predict and vary widely. Accordingly, the application of a universal photoresist pattern to the surface of a pole-tip assembly is a generalized solution that often is ill suited to the actual manufacturing defect of any one recording transducer. Therefore, current techniques for producing a magnetic recording transducer have several serious limitations with respect to control of pole-tip assembly geometry.
Consequently, higher density data storage devices can require micromachining of the recording transducer used with the devices. Manufacturers can micromachine the recording transducer while it is contained in a multi-layer device. Prior to micromachining, a multi-layer device is lithographically fabricated. Once the multi-layer device is fabricated, it is cleaved at a selected location and the cleaved surface is polished to expose at least one recording transducer pole-tip assembly formed by the multi-layer device.
The micromachining of a recording transducer can require accurate shaping of a write head. However, the read head can employ a sensitive structure such as a Magneto-Resistive Stripe (MRS). A MRS can suffer damage as a result of irradiation by a focused ion beam (FIB). For background information on the design and function of a MRS and an inductive write head, see the text "Magneto-Resistive Heads, Fundamentals and Applications" by John C. Mallinson (Academic Press, Inc., San Diego 1996), incorporated herein by reference. It is important to note that the MRS and the write head can each have sublayers. An MRS can include thin-film sublayers, each five to six angstroms thick. The properties of a read head, including a MRS, can be altered during irradiation by a focused ion beam (FIB). Thus, there is a need for focused ion beam systems and methods that locate and accurately shape a write head without irradiating a read head of a pole-tip assembly of a thin-film magnetic recording transducer.
Accordingly, it is an object of the present invention to provide apparatus and methods for manufacturing improved thin-film magnetic recording transducers using a focused particle beam.
It is a further object of the present invention to precisely form the pole-tip assembly of a magnetic recording transducer without irradiating a sensitive structure, e.g., a read head, in the recording transducer.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention is described herein in connection with certain embodiments; however, it will be clear to those skilled in the art of magnetic recording transducer manufacture that various modifications, additions and subtractions can be made to the described embodiments without departing from the spirit or scope of the invention.